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LETTERS TO THE EDITOR

Popliteal Block as an Alternative to Labat’s Approach

Anesthesia Unit, Fundación Hospital Alcorcón, Madrid, Spain

To the Editor:

I read with interest the article by di Benedetto et al. (1) on the comparison of a new subgluteus approach to the sciatic nerve block versus Labat’s approach. I agree that Labat’s technique has its shortcomings, but I believe there are better alternatives than this subgluteus technique.

Popliteal block (PB) also provides a rapid, effective, and safe anesthesia (2). Several posterior and lateral approaches to the sciatic nerve at this level have been described (3–5). Anatomic landmarks are easily recognized; moreover, there is usually less adipose tissue in the popliteal region than in the gluteal or subgluteal regions, and this could be an advantage in obese patients. During posterior PB performance, the needle rarely passes through the biceps femoris; the lateral approach might be associated with more patient discomfort because of the needle passage through the biceps femoris or vastus lateralis muscles (tendons). Premedication, low-intensity stimulation and anesthetic local infiltration nearly always prevent patient discomfort. I would also like to emphasize that the need to position the patient in the lateral decubitus position may preclude or make difficult the use of the authors’ technique in patients who could benefit the most from a sciatic block (e.g., in cases of spinal and hemodynamic instability or mechanical ventilation). The lateral approach to the PB allows its performance in the supine position and provides the option of performing supplementary blocks (saphenous or femoral nerve) and surgery without the need for patient repositioning. Is the subgluteus posterior block indeed the best alternative to the Labat’s approach disregarding the PB?

References

1. Di Benedetto P, Bertini L, Casati A, et al. A new posterior approach to the sciatic nerve block: a prospective, randomized comparison with the classic posterior approach. Anesth Analg 2001; 93: 1040–4.[Abstract/Free Full Text]
2. Fernández-Guisasola J, Andueza A, Burgos E, et al. A comparison of 0.5% ropivacaine and 1% mepivacaine for sciatic nerve block in the popliteal fossa. Acta Anaesthesiol Scand 2001; 45: 967–70.[Web of Science][Medline]
3. Rorie DK, Byer DE, Nelson DO, et al. Assessment of block of the sciatic nerve in the popliteal fossa. Anesth Analg 1980; 59: 371–76.[Abstract/Free Full Text]
4. Collum CR, Courtney PG. Sciatic nerve blockade by a lateral approach to the popliteal fossa. Anaesth Intensive Care 1993; 21: 236–7.
5. Hadzic A, Vloka J. A comparison of the posterior versus lateral approaches to the block of the sciatic nerve in the popliteal fossa. Anesthesiology 1988; 88: 1480–86.

Response

Department of Anesthesiology, Vita-Salute University of Milano, IRCCS San Raffaele Hospital, Milan, Italy Department of Anesthesiology, CTO Roma, Rome, Italy

In Response:

We would like to thank Dr. Fernàndez-Guisasola for his interest in our work (1) as well as his practical comments, which remind us once more, if needed, that the sciatic nerve can be blocked at several levels along its pathway with a lot of "different" posterior and lateral approaches. Popliteal blocks undoubtedly provide a good and effective anesthesia (2,3). In our daily practice we use them frequently, not only for single shot blockades but also for postoperative pain relief, by placing a perineural catheter close to the sciatic nerve and infusing it with local anesthetic solutions after surgery (4).

Nonetheless, Dr. Fernàndez-Guisasola should recognize that the aim of our study was "to describe a new posterior approach to the sciatic nerve at the level of the proximal thigh and compare. . .the effectiveness, performance time, and patient’s acceptance of this new approach with the classic posterior approach" (1). In fact, results of our study demonstrated that this new posterior approach is easier and less painful to the patient as compared to the classic Labat’s approach only. This allows us to suggest that the subgluteus sciatic nerve block can be considered a useful alternative to Labat’s approach, but we never stated that the sublguteus posterior block is the best alternative to the Labat’s approach, disregarding the popliteal blocks.

On the other hand, we must also consider that the Dr. Fernàndez-Guisasola’s hypothesis that the posterior popliteal block is easier than other approaches in the obese patient is as much theoretical as intriguing, and it is not supported by properly conducted, randomized studies. Irrespective from discussing the distribution of adipose tissues in the obese patient, what about turning prone an obese patient to place the block and then turning it back to the supine position? Further, very often a more proximal approach than the popliteal one is required because of surgical site (e.g., surgery at the level of the knee) or surgeon’s needs (e.g., thigh tourniquet). However, this is a matter of other new studies, and we look forward to reading them to better understand the best indication for each approach to the sciatic nerve according to both patient and surgery.

In conclusion, we completely agree with Dr. Fernandez-Guisasola that the physician must choose and titrate the best nerve block according to patient characteristics, the type of surgery, and the surgeon’s needs. However, personal skills and expertise also play an important role: the more techniques we know and practice, the more flexible is our practice, helping us to get all the benefits of peripheral nerve blocks in different clinical situations. In this view, the description of our new posterior approach to the sciatic nerve is only an attempt to improve the comfort of both the patient and physician when a proximal sciatic nerve block is required: just another arrow in our quiver.

References

1. di Benedetto P, Bertini L, Casati A, et al. A new posterior approach to the sciatic nerve block: a prospective, randomized comparison with the classic posterior approach. Anesth Analg 2001; 93: 1040–4.
2. Fernàndez-Guisasola J, Andueza A, Burgos E, et al. A comparison of 0.5% ropivacaine and 1% mepivacaine for sciatic nerve block in the popliteal fossa. Acta Anaesthesiol Scand 2001; 45: 967–70.
3. Hadzic A, Vloka J. A comparison of the posterior versus lateral approaches to the block of the sciatic nerve in the popliteal fossa. Anesthesiology 1998; 88: 1480–6.[Web of Science][Medline]
4. Casati A, Chelly JE, di Benedetto P, Fanelli G. Sacral plexus and sciatic nerve. In: Chelly JE, Casati A, Fanelli G, eds. Continuous peripheral nerve block techniques: an illustrated guide. Milano: Mosby, 2001: 67–80.

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